Build process tries to build assistant even if webkit is disabled; compile fails

Building qt (current 4.8 branch) with -no-webkit fails:

helpviewer_qwv.cpp:168:1: error: expected class-name before '{' token
helpviewer_qwv.cpp:173:13: error: 'QWebPage' does not name a type
helpviewer_qwv.cpp:174:32: error: 'WebAction' has not been declared
helpviewer_qwv.cpp:176:42: error: 'QWebFrame' has not been declared
helpviewer_qwv.cpp:177:41: error: 'NavigationType' has not been declared
helpviewer_qwv.cpp: In constructor 'HelpPage::HelpPage(QObject*)':
helpviewer_qwv.cpp:189:7: error: class 'HelpPage' does not have any field named 'QWebPage'
helpviewer_qwv.cpp: At global scope:
helpviewer_qwv.cpp:197:1: error: 'QWebPage' does not name a type
helpviewer_qwv.cpp:207:30: error: variable or field 'triggerAction' declared void
helpviewer_qwv.cpp:207:30: error: 'WebAction' was not declared in this scope
helpviewer_qwv.cpp:207:48: error: expected primary-expression before 'bool'
make[4]: *** [.obj/release-shared-emb-x86_64/helpviewer_qwv.o] Error 1
make[4]: *** Waiting for unfinished jobs....
make[4]: Leaving directory `/usr/src/ark/BUILD/qt/tools/assistant/tools/assistant'

Assistant could either fall back to displaying stuff in a QLabel (probably good enough for the basic HTML in the docs?) or be excluded from the build if -no-webkit is given.